(a) Field of the Invention
This invention relates to an optical information recording medium comprising a substrate having a cured under-layer of a light curable resin thereon.
(b) Description of the Prior Art
Heretofore, there are known injection process and photo-polymerization process (Philips tech. Rev., Vol. 40, pp. 298-309, 1982) as a process for forming a concavo-convex pattern information track on a substrate. However, a light memory disk prepared by the injection process causes much noise because reflected light varies due to double refraction. Furthermore, since this memory disk has poor resistance to solvents, there is the possibility that a pre-groove may be lost when a reflective layer, recording layer, protective layer and the like are formed on the information track by a wet coating process. Still furthermore, when making use of metallic light reflection by coloring matter as a recording material, various performances of focusing, tracking, regenerating signals and the like of a recording and regenerating device are badly affected because reflectivity, particularly reflectivity through the substrate is lowered due to solvent attack on the pre-groove.
On the other hand, when a pre-groove is formed by the photo-polymerization process using base polymer, diluent, photo-polymerization initiator and the like, the above mentioned double refraction and solvent resistance problems are removed, but the preservability of a thin film recording layer is poor. Thus, pinholes occur due to degradation by light and heat, and accordingly reflectivity and light absorbency are lowered.